[Dopamine-beta-hydroxylase (DBH)].
Explore the source record for details and available documents.
Adolescent↗
Biomedical subjects
T Nakai
Publications and source records attributed to T Nakai.
Increase in neutral cholesteryl ester hydrolase activity produced by extralysosomal hydrolysis of high-density lipoprotein cholesteryl esters in rat hepatoma cells (H-35).
The metabolism of high-density lipoprotein-associated cholesteryl esters (HDL-CE) in liver cells is not well understood. We studied the possible role of lysosomal and extralysosomal pathways on such metabolism by measuring the uptake and hydrolysis of HDL-CE in H-35 rat hepatoma cells. Incubation of cells with [3H]cholesteryl ester-labeled HDL led to the intracellular accumulation of both 3H-free cholesterol and [3H]cholesteryl ester. The ratio of 3H-free cholesterol/[3H]cholesteryl ester increased with an increase in incubation time even in the presence of chloroquine. Because chloroquine did not inhibit the conversion of cholesteryl ester to free cholesterol, the hydrolysis of HDL-CE may have been catalyzed by an extralysosomal enzyme, perhaps by neutral cholesteryl ester hydrolase (NCEH). When we incubated cells with increasing concentrations of HDL, NCEH activity increased. This increase in enzyme activity was not inhibited by the addition of chloroquine. A complex of dimyristoylphosphatidylcholine (DMPC)/apo HDL/cholesteryl ester enhanced the activity as well as native HDL. Neither the DMPC/apo HDL nor the DMPC/cholesteryl ester complex affected the activity, suggesting that apo HDL may be required for the uptake of HDL-CE. The present study demonstrated that the extralysosomal hydrolysis by NCEH is operating in the metabolism of HDL-CE in hepatoma cells.
Animals↗
Extracorporeal shock wave lithotripsy (ESWL) for biliary stones: a nationwide survey in Japan.
To assess the current status of extracorporeal shock wave lithotripsy (ESWL) for the treatment of gall-stones in Japan, we conducted a nationwide survey by sending a questionnaire to 251 institutions using this therapy. Replies were obtained from 50 institutions. The use of ESWL was investigated over the period from its introduction up to October 1992. ESWL was performed on 2,760 of 10,058 patients with gallstones (27.4%). The stones were completely pulverized in 1,021 of these 2,760 patients (37.0%). Complete disappearance was limited to single gallstones less than 20 mm in maximum diameter. A comparison in the number of ESWL sessions revealed no significant difference between the patients with and without a good response. Choledocholithiasis was resolved completely in 44.0% of 157 patients who underwent ESWL for this condition and intrahepatic stones were cured in 18.7% of 32 patients. Therefore, ESWL may be a useful form of conservative therapy for biliary calculi.
Cholelithiasis↗
Influence of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors on mitochondrial respiration in rat liver during ischemia.
Effects of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, pravastatin and simvastatin, on mitochondrial respiration in ischemic rat liver were examined. Either vehicle, pravastatin (2 or 4 mg/kg per day), or simvastatin (1 or 2 mg/kg per day) was orally administered for 3 weeks. Liver ischemia was induced by cessation of the systemic circulation for 60 min. Liver mitochondria were isolated and the respiration was determined by polarography using glutamate and succinate as substrates. In the vehicle-treated group, ischemia drcreased ZO3, respiratory control index (RCI: QO3/QO4), and ADP/O ratio. Pretreatments with pravastatin and simvastatin enhanced the decreases in QO3 measured with either glutamate or succinate, and in ADP/O ratio measured with succinate. Because of decreasing QO4, HMG-CoA reductase inhibitors did not modify the changes in RCI due to ischemia. There were no significant differences in respiratory indices between pravastatin- and simvastatin-treated groups. In conclusion, HMG-CoA reductase inhibitors may enhance respiratory impairment of liver mitochondria under pathophysiological conditions, such as ischemia.
Adenosine Diphosphate↗
Aminopeptidase Y, a new aminopeptidase from Saccharomyces cerevisiae. Purification, properties, localization, and processing by protease B.
A novel aminopeptidase, termed aminopeptidase Y, was purified from yeast, Saccharomyces cerevisiae, as two molecular forms of 70 and 75 kDa, which were identical immunologically, catalytically and in N-terminal sequence up to 14 residues. They contained 0.81 and 0.84 mol of zinc atom/mol of protein, respectively. N-Gly-canase generated a single 53-kDa species from both forms, and endoglycosidase H gave a 54-kDa species. Immunoblotting after subcellular fractionation showed that aminopeptidase Y is localized in the vacuole/lysosome-soluble compartment as the 70-kDa form. Aminopeptidase Y hydrolyzed all amino acid-4-methylcoumaryl-7-amides (MCA) examined, especially Lys- and Arg-MCA. Dipeptidyl-MCAs were far more rapidly hydrolyzed (Lys-Ala-MCA/Lys-MCA = 350-fold, Arg-Arg-MCA/Arg-MCA = 150-fold). Hydrolysis of amino acid-MCAs or dipeptides was markedly enhanced by Co2+, whereas that of dipeptidyl-MCAs, tripeptides, and larger peptides was inhibited. Rabbit anti-aminopeptidase Y antiserum adsorbed over half the aminopeptidase activities in vacuolar extract from wild-type yeast cells. ABYS1 mutant cells from which the genes of four vacuolar proteases had been deleted contained aminopeptidase Y as a 74-kDa proform. This was converted to the mature form (70 kDa) by vacuolar extract of wild-type cells and by purified yeast vacuolar protease B.
Amino Acid Sequence↗
Molecular cloning of the aminopeptidase Y gene of Saccharomyces cerevisiae. Sequence analysis and gene disruption of a new aminopeptidase.
A yeast genomic DNA encoding a new vacuolar aminopeptidase, aminopeptidase Y, was isolated by using a cDNA fragment obtained by screening the lambda gt11 yeast cDNA library with anti-aminopeptidase Y antibody. The DNA sequence encodes 537 amino acids. The "mature" protein, whose NH2-terminal sequence was determined previously by analysis of the purified enzyme, consists of 481 amino acids, and the calculated molecular weight (52,900) coincides with the value obtained by SDS-polyacrylamide gel electrophoresis of the enzyme after removal of sugar chains, 53 kDa. The 56-residue preprosequence was divided into two parts by putative processing sites for signal peptidase and conversion to the mature form; the 21-residue presequence has a hydrophobic stretch which may function as the signal sequence for transit through the endoplasmic reticulum, and the 35-residue prosequence (4013 Da) accounts for the 4-kDa difference between proaminopeptidase Y in the vacuolar proteases-deleted ABYS1 mutant and wild-type mature enzyme. The aminopeptidase Y gene was localized on chromosome II by genetic mapping. A deletion mutant was constructed by disrupting the aminopeptidase Y gene. Vacuolar aminopeptidase activities toward Ala-4-methylcoumaryl-7-amide (MCA) and Lys-MCA were 13 and 20% of wild-type, and those in the presence of Co2+ were 2.2 and 2.8%, respectively. Mutant cells showed no ability to hydrolyze Lys-Ala-MCA to Lys and Ala-MCA, although vacuolar carboxypeptidase Y activity was similar to that in wild-type cells.
Amino Acid Sequence↗
Solution structure of a de novo helical protein by 2D-NMR spectroscopy.
The de novo design of proteins represents a critical test for our knowledge of protein structure. However, no structure of a successfully designed protein has yet been reported. This paper reports the design and the tertiary structure of a de novo 35-residue helix-loop-helix protein (ALIN), with helices arranged in an anti-parallel manner. For the helical region, we designed sequences that have high helicities even as isolated peptides. A flexible loop containing glycine residues was used to connect the two helices and the interhelical hydrophobic interaction was stabilized by the introduction of an SS-bridge. This arrangement of two consecutive helices bridged by a disulfide bond is not observed in any natural proteins. The protein is highly soluble and monomeric in aqueous solution. The structure of ALIN, determined by 1H-NMR and distance geometry calculation, agrees well with the design. In addition, the exchange rates of amide protons indicate the presence of stable hydrogen bonds in the helical region. ALIN is the first de novo designed protein with a stable tertiary fold confirmed by NMR.
Amino Acid Sequence↗
Effect of intrahepatic portal-systemic shunting on hepatic ammonia extraction in patients with cirrhosis.
Increased plasma ammonia levels in patients with advanced cirrhosis have been attributed to reduced conversion of enteric ammonia to urea by the diseased liver and to entry of enteric ammonia into systemic circulation by way of portal-systemic shunts. Because single-pass extraction is high for portal venous ammonia, reduction of portal blood supply to hepatocytes may have detrimental effects on the hepatic extraction of ammonia. To assess how the development of intrahepatic portal-systemic shunts alters hepatic ammonia metabolism, we determined portal and hepatic venous ammonia levels along with measurements of intrahepatic portal-systemic shunts using 99mTc-macroaggregated albumin in 46 patients with portal hypertension. Hepatic venous ammonia levels in the groups of patients with idiopathic portal hypertension, Child class A cirrhosis and Child class B or C cirrhosis were 36 +/- 17, 75 +/- 26 and 93 +/- 52 micrograms/dl, respectively, in increasing order, and portal venous ammonia extraction rates as calculated with the equation (portal venous ammonia-hepatic venous ammonia)/portal venous ammonia x 100% were decreased in the same order (77% +/- 14%, 50% +/- 21%, 40% +/- 25%, respectively). Furthermore, we noted a significant negative correlation between the intrahepatic shunt indexes as calculated by counts per minute in lungs/counts per minute in lungs and liver x 100% and the ammonia extraction rates. It was noteworthy that among Child class C patients, the ammonia extraction rates were significantly lower in patients with high intrahepatic shunt indexes than in those with low shunt indexes. These results demonstrate a significant direct relationship between hepatic ammonia extraction rates and intrahepatic shunting in cirrhosis.
Adult↗
Effect of diazoxide on serum and tissue electrolyte levels in rats with deoxycorticosterone acetate-induced hypertension.
Effects of diazoxide, a benzothiadiazine derivative, on the blood pressure, excretion of Na+, K+, and Ca2+, and the levels of these electrolytes in serum, kidney, and aorta were studied in rats with deoxycorticosterone acetate (DOCA)-induced hypertension in comparison with rats treated with hydrochlorothiazide. After a lateral nephrectomy, 5 mg kg-1 of DOCA was injected subcutaneously three times a week. Drinking water for the rats injected with DOCA contained 1% NaCl. Systolic blood pressure in the DOCA-induced hypertensive rats became about 170 mmHg, with associated elevation of serum level of Na+ 7 weeks after the treatment, whereas that in the normotensive rats was about 100 mmHg. In the DOCA-hypertensive rats, urinary output, and renal excretion of Na+ and Ca2+ increased, and aortic tissue level of Ca2+ decreased as compared with those in the normotensive rats. After 7 weeks of the treatment, diazoxide (10 mg kg-1) or hydrochlorothiazide (10 mg kg-1) was injected intravenously. Diazoxide decreased the blood pressure in both DOCA-hypertensive and normotensive rats, whereas hydrochlorothiazide decreased it only in the DOCA-hypertensive rats. Diazoxide recovered the tissue aortic Ca2+ level that had been decreased by hypertension to that in the normotensive rats. Diazoxide may improve Ca2+ perturbation in the vascular smooth muscle due to DOCA-induced hypertension.
Animals↗
Effects of diazoxide on KCl- and norepinephrine-induced contraction in isolated rat aorta.
Diazoxide produced endothelium-independent relaxations of the rat aorta contracted by either low concentrations of KCl or norepinephrine (NE). However, contraction with a high concentration of KCl was not altered by diazoxide. Hydrochlorothiazide did not affect the contraction induced by either KCI or NE. Tetraethylammonium and glibenclamide inhibited the relaxations of the aorta induced by diazoxide. Diazoxide significantly reduced the phasic and tonic contractions under Ca2+-free conditions induced by NE and CaCl2 following NE addition, respectively. These results suggest that diazoxide dilates vascular smooth muscle by opening the ATP-sensitive K+ channels and inhibiting receptor-operated Ca2+ movements from either the intracellular store sites or extracellular space to the cytoplasm, but not antagonizing voltage-dependent Ca2+ channels directly.
Animals↗
Diltiazem inhibits DNA synthesis and Ca2+ uptake induced by insulin, IGF-I, and PDGF in vascular smooth muscle cells.
Proliferation of vascular smooth muscle cells (VSMC) has been shown to play a key role in the atherosclerotic lesions. It has been demonstrated that serum-derived peptidic growth factors, such as insulin, platelet-derived growth factor (PDGF), or epidermal growth factor (EGF), provide mitogenic signals in VSMC and that the interplay of Ca2+ and other messengers is necessary for triggering proliferation. Since Ca2+ channel blockers act on the voltage-dependent Ca2+ channel to inhibit Ca2+ influx, it is conceivable that they affect the proliferative action of growth factors. In this study we have evaluated the effects of diltiazem, a 1,5-benzothiazepine-derived Ca2+ channel blocker, on [3H]thymidine incorporation into DNA stimulated by insulin, insulinlike growth factor I (IGF-I), or PDGF in cultured VSMC from rat aorta. We have also investigated the effects of insulin, IGF-I, and PDGF on Ca2+ uptake in VSMC. After exposure to insulin (10(-10) to 8 x 10(-6) M) or IGF-I (10(-10) to 10(-7) M) for 48 hours, VSMC incorporated [3H]thymidine to 200-280% of maximum (with insulin or IGF-I alone) compared to control. The effect of IGF-I was approximately 10-100 times more potent than that of insulin. PDGF (0.5-15 ng/ml) also induced an increase in [3H]thymidine incorporation into DNA of VSMC. Additivity is observed between PDGF with insulin or IGF-I, but not between insulin and IGF-I. Sixty minute treatment with insulin (5 x 10(-8) to 10(-6) M), IGF-I (10(-8) to 10(-6) M), or PDGF (1.0-15.0 ng/ml) increased the unidirectional 45Ca2+ uptake during a 5 minute period.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Acute abdominal symptoms caused by hemorrhagic necrosis of a pheochromocytoma: report of a case.
The diagnosis of pheochromocytoma is often difficult in a patient presenting with acute illness but without the classical constitutional symptoms. We report herein the case of a woman who developed acute abdominal symptoms following hemorrhagic necrosis of a previously unsuspected pheochromocytoma. This patient underwent successful emergency resuscitation followed later by elective surgical resection of a right adrenal pheochromocytoma. A review of 27 other cases indicates that a fatal outcome is likely to result without the initiation of prompt and appropriate emergency treatment, followed later by removal of the tumor. Thus, early diagnosis is important not only for controlling hypertension, but also because performing a laparotomy on a patient with unrecognized hemorrhagic necrosis of pheochromocytoma can create a potentially lethal situation.
Abdomen, Acute↗
Pituitary adenylate cyclase-activating polypeptide: effects on pancreatic-adrenal hormone secretion and glucose-lipid metabolism in normal conscious dogs.
The effects of pituitary adenylate cyclase-activating polypeptide (PACAP) on plasma insulin, glucagon, catecholamine, cortisol, glucose, triglyceride (TG), free fatty acid (FFA), cholesterol, and cyclic adenosine monophosphate (cAMP) concentrations were examined in unanesthetized normal dogs. A bolus injection of 6 pmol/kg PACAP27 elicited a transient increase in plasma insulin, epinephrine, and norepinephrine concentrations, with a peak value at 2 minutes after injection. Injections of 60 and 600 pmol/kg caused greater increases in these hormone concentrations in a dose-dependent manner. The plasma cortisol concentration was not changed by a bolus injection of 6 pmol/kg PACAP27, and was gradually increased by injections of 60 and 600 pmol/kg. Significant increases were observed from 10 and 5 minutes after the injection of 60 and 600 pmol/kg, respectively. The plasma glucagon concentration was not changed by either 6, 60, or 600 pmol/kg. The plasma glucose concentration decreased with 60 pmol/kg PACAP27 and increased with 600 pmol/kg. The plasma FFA concentration was increased gradually, with a peak value at 10 minutes after the injection, in a dose-dependent manner. The plasma TG concentration was slightly increased with 600 pmol/kg with a peak value at 10 minutes, although plasma cholesterol did not change. The plasma cAMP concentration increased significantly with 600 pmol/kg PACAP27, but not with 6 or 60 pmol/kg. These effects of PACAP27 were observed with a bolus injection of PACAP38 of an equal potency. Infusion of graded doses of PACAP27 (1, 3, and 10 pmol/kg/min every 20 minutes) caused a gradual increase in plasma cortisol, catecholamine, FFA, and cAMP concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Pertussis toxin pretreatment enhances catecholamine secretion induced by pituitary adenylate cyclase-activating polypeptide in cultured porcine adrenal medullary chromaffin cells: a possible role of the inositol lipid cascade.
We determined how pertussis toxin (PTX) pretreatment alters PACAP-induced catecholamine secretion in cultured porcine adrenal medullary cells. Pretreatment of these cells with PTX (1 ng/ml for 24 h or 10 ng/ml for 6 h) markedly enhanced PACAP-induced catecholamine secretion. PTX pretreatment also produced a small increase in basal secretion and secretion in response to nicotine and carbachol, but the effect of the PACAP-induced secretion was most striking. We examined the role of the phosphoinositol cascade in potentiating the PACAP-induced catecholamine secretion by PTX and found that PACAP-induced accumulation of inositol phosphates in PTX-pretreated cells was significantly greater than that in untreated cells. Furthermore, removal of extracellular Ca2+ and addition of Ca2+ channel blockers inhibited the catecholamine secretion induced by PACAP in PTX-pretreated cells. From these results, we speculate that a PTX-sensitive G-protein tonically inhibits phospholipase C. PTX enhances the PACAP-induced secretion of catecholamine by blocking the action of this inhibitory G-protein.
Adenylate Cyclase Toxin↗
Effects of chronic diabetes on the responsiveness to endothelin-1 and other agents of rat atria and thoracic aorta.
1. Plasma endothelin-1 level as well as plasma lipid and glucose levels was markedly elevated in the rats treated with streptozotocin 8 weeks earlier. 2. Positive inotropic response, which was significantly greater than that in the age-matched control, was produced by endothelin-1 in the left atria isolated from diabetic rats. On the other hand, the contractile response of thoracic aorta to endothelin-1 was conversely attenuated in the diabetic rats. Such contrasting effects of diabetes between the atrial and aortic muscles were observed in the responsiveness to other contractile drugs. Endothelium-dependent relaxation in the thoracic aorta was also significantly attenuated in diabetic rats. However, the basal twitch contraction of left atria, the chronotropic responses to endothelin-1, isoproterenol and carbachol and the relaxation of the aorta by papaverine were not affected by diabetes. 3. These results suggest that the contractile responsiveness of atrial and aortic muscles and the endothelial functions significantly alter during diabetes for 8 weeks.
Animals↗
Clinical features of hepatocellular carcinoma in the elderly: a study of 91 patients older than 70 years.
In order to determine the clinical features of hepatocellular carcinoma in the elderly, a total of 622 patients with hepatocellular carcinoma, including 91 patients 70 years or older, were retrospectively analysed with reference to their ages at the time of diagnosis. The proportion of females increased and that of hepatitis B surface antigen-positive cases decreased as age increased. Tumour sizes at the time of diagnosis were somewhat smaller in the elderly than in younger patients, whereas clinical stage taking liver function into consideration was similar in the two age groups. The prognosis in the elderly patients was similar to that in the younger ones in a clinical stage-matched comparison. Furthermore, by a multivariate analysis using the Cox proportional hazards model with inclusion of age and other clinical parameters, age was not selected in the final model as an independent predictor for survival. These results indicate that elderly patients with hepatocellular carcinoma have certain clinical features different from those in younger patients and that their prognosis is not necessarily poorer than in the latter.
Adolescent↗
ATP-dependent proteolysis in yeast mitochondria.
An ATP-dependent proteolysis system in yeast mitochondria was characterized by examining the hydrolysis of mitochondrial translation products in isolated mitochondria. Degradation of [35S]methionine-labeled polypeptides synthesized in isolated yeast mitochondria was activated by exogenously added ATP. ADP, GTP, and CTP substituted for ATP to some extent, but nonhydrolyzable ATP analogues did not. Adenosine-5'-O-(3'-thio-triphosphate) effectively competed with ATP as activator. Carboxyatractyloside, an inhibitor of adenine nucleotide translocation across the mitochondrial inner membrane, and the metal chelator o-phenanthroline inhibited the ATP-dependent proteolysis. The latter inhibition was abolished by subsequent addition of Mn2+ or Co2+ but not Ca2+ or Zn2+. Hemin inhibited the ATP-dependent proteolysis of mitochondrial translation products with a half-maximum inhibition at 12 microM. Analysis by SDS-polyacrylamide gel electrophoresis showed that [35S]methionine-labeled polypeptides were rapidly degraded into low-molecular-weight species. Submitochondrial particles retained the ATP-dependent proteolytic activity and had the same spectrum of inhibitors as intact mitochondria except for a reduced effect of carboxyatractyloside. These results indicate that yeast mitochondria contain an ATP-dependent and hemin-sensitive proteolysis system which is associated with the inner membrane and can hydrolyze mitochondrial translation products, and that a chelator-sensitive protease is probably involved in this system.
Adenosine Triphosphate↗